The present invention relates to a blower, and more particularly to a tangential blower including a rotor, a spiral-shaped baffle plate which passes from the spiral shape into a plane portion in the region of the high-pressure side and, after its closest approach to the rotor at the high-pressure side, extends away from the rotor at the low-pressure side in a sharp bend. The blower also includes end plates and a vortex-forming system which separates the low-pressure side from the high-pressure side. The system includes two or more guidewalls whose edges extend transversely to the direction of flow, are straight over their entire lengths and are parallel to the blade edges of of the rotor. The guidewalls form passages that converge toward the rotor and are open at both ends.
Tangential blowers are known, e.g. from Belgian Pat. No. 599,024, whose rotors have a twisted, helical, swept-back or axially staggered blading to reduce the noise of the blades. They are very expensive to manufacture.
German Printed Application No. 1,277,505 describes tangential blowers wherein the distance between the rotor and the baffle plate inlet edge and/or the inside edge of the vortex former is enlarged to reduce the blower noise. This causes considerable pressure losses.
Various other prior art blower designs with or without the use of recirculation are known from, e.g., German Printed Applications Nos. 1,428,071, 1,503,668 and 1,503,673, German Published Applications Nos. 1,951,115, 2,030,837 and 2,048,541 and from German Petty Patent No. 1,980,832. Unless provided with expensive control elements, each of those blowers can only be operated either with or without the use of recirculation and, therefore, has only one throttling characteristic .psi. = f (.phi.) which corresponds to its construction. In this equation, .psi. is the pressure figure, and .phi. the delivery figure.
Each of the above-mentioned blowers can have its low- or high-pressure side connected to only one cross section without loss of efficiency unless expensive connections are used. None of these blowers suppresses bothersome blade noise over a sufficiently wide throttling range. The field of application thereof thus remains limited.